This invention relates generally to compositions of soy protein isolates and caseinate which exhibit desirable functional properties. Also, this invention relates to a method of combining caseinate with soy protein isolate so that the previously mentioned desirable functional properties are imparted to the soy and thereby permit its use in coffee whiteners where it was heretofore unsuitable. Prior to the present invention, the principal proteinaceous ingredient in coffee whiteners was neutralized casein which is generally referred to as caseinate. However casein is a milk-derived protein. Unfortunately milk, like other dairy products, is becoming increasingly more scarce and more expensive. Therefore a need has developed for replacing the more expensive milk-derived protein casein with a more plentiful and less expensive protein, such as soy protein. Although attempts have been made to work soy protein into dairy formulations in the past, these attempts required cumbersome and costly modification of the soy protein. For example, U.S. Pat. Nos. 3,642,493 and 3,642,492 call for physico-thermo-vapor flash pretreatment of the isolated soy protein and combining it with certain levels of whey solids; U.S. Pat. No. 3,764,711 calls for chemically modifying the soy isolate molecular structure by addition of an acyl bearing anhydride group. It is of note however, that the functionality of even these isolates can be improved by the instant invention. Prior to the present invention no attempt was made to merely combine commercially available soy protein isolates (which had not undergone these special treatments e.g. U.S. Pat. No. 3,764,711 ) with caseinate because there was no known interaction between the two which corrects the deficiency of the soy protein isolate. The principle characteristic deficiency of soy protein isolate which makes it unsuitable for coffee whiteners is "feathering". "Feathering" is a term used in the art to describe the situation where the protein contacts substantial concentrations of coffee, tea and beverages of similar composition and as a consequence thereof precipitates, aggregates or becomes insoluble. Soy protein isolates will feather no matter what quantity is used if the soy is used alone. This may be due to caffeic, chlorogenic and/or tannic acids, therein, which are capable of forming salts or complexes with basic amino functional groups of the protein, i.e., epsilon amino groups, so as to cause precipitation. Therefore it would not seem possible that merely dry blending with caseinate, a soy protein isolate which exhibits this chemical deficiency would in any way affect the characteristics which cause feathering. Also, most water soluble proteins tend to coagulate when subjected to heat. Proteins other than soy protein isolates, such as even casein, sodium caseinate, etc., when used in coffee whitener formulations, also are subject to such feathering or other non-functionality under some conditions, such as when utilized in amounts less than a prescribed minimum or when subjected to certain harsh coffee environments such as with freeze-dried instant coffee.
Accordingly a simple yet uniquely effective means for adapting soy protein isolates to coffee whitener compositions and for substantially reducing the amount of caseinate would represent a substantial advancement of the art.